Please answer: Calculate the correct rate of heat loss through the vertical walls of a boiler furnace of size 4 m by 3 m by 3 m high (A=12 m ). The walls are constructed from an inner fire brick wall 25 cm thick of thermal conductivity 0.4 W/mK, a 2 mm thick steel protective layer of thermal conductivity 55 W/mK, and a layer of ceramic blanket insulation of thermal conductivity 0.2 W/mK and 8 cm thick. The inside temperature of the fire bricklayer was measured at 600 deg C and the temperature of the outside of the insulation 60 deg C.

Please answer: Calculate the correct rate of heat loss through the vertical walls of a boiler furnace of size 4 m by 3 m by 3 m high (A=12 m ). The walls are constructed from an inner fire brick wall 25 cm thick of thermal conductivity 0.4 W/mK, a 2 mm thick steel protective layer of thermal conductivity 55 W/mK, and a layer of ceramic blanket insulation of thermal conductivity 0.2 W/mK and 8 cm thick. The inside temperature of the fire bricklayer was measured at 600 deg C and the temperature of the outside of the insulation 60 deg C.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.10P: 1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss...

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2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.
1.1 On a cold winter day, the outer surface of a 0.2-m-thick concrete wall of a warehouse is exposed to temperature of –5°C, while the inner surface is kept at 20°C. The thermal conductivity of the concrete is 1.2 W/m K. Determine the heat loss through the wall, which is 10-m long and 3-m high. Problem 1.1
1.37 Mild steel nails were driven through a solid wood wall consisting of two layers, each 2.5-cm thick, for reinforcement. If the total cross-sectional area of the nails is 0.5% of the wall area, determine the unit thermal conductance of the composite wall and the percent of the total heat flow that passes through the nails when the temperature difference across the wall is 25°C. Neglect contact resistance between the wood layers.
2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)
An electronic device that internally generates 600 mW of heat has a maximum permissible operating temperature of 70C. It is to be cooled in 25C air by attaching aluminum fins with a total surface area of 12cm2. The convection heat transfer coefficient between the fins and the air is 20W/m2K. Estimate the operating temperature when the fins are attached in such a way that (a) there is a contact resistance of approximately 50 K/W between the surface of the device and the fin array and (b) there is no contact resistance (in this case, the construction of the device is more expensive). Comment on the design options.
2.45 Heat is transferred from water to air through a brass wall . The addition of rectangular brass fins, 0.08 cm thick and 2.5 cm long, spaced 1.25 cm apart, is contemplated. Assuming a water-side heat transfer coefficient of and an airside heat transfer coefficient of , compare the gain in heat transfer rate achieved by adding fins to (a) the water side, (b) the air side, and (c) both sides. (Neglect temperature drop through the wall.)
3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.
16. A steel pipe 1.5-m in length has an inside diameter of 7.6 cm with a wall thickness of 11.6 mm. The steel has a thermal conductivity of 46 W/m K. The pipe is covered with a 4 cm thick layer of insulation with a thermal conductivity of 0.4 W/m K. What is the total thermal resistance from the inside surface of the pipe to the outside surface of the insulation layer? Express your answer in °C/W or K/W.
A thick-walled tube of stainless steel with thermal conductivity k=19 W/m°C has inner diameter of 10 cm and outer diameter of 30 cm covered with 5 cm layer of asbestos insulation with thermal conductivity k= 0.2 W/m°C. If the inside of the pipe and outside of insulator temperature is maintained at 600°C and 107°C respectively. Determine the heat loss per meter length of pipe and the tube-insulation interface temperature.
The wall of a furnace consists of 200 mm thick refractory brick (k = 3 Btu / hr-ft2-0F), 100 mm thick bricks (k = 0.050 Btu / hr-ft2-0F) and 6 mm thick steel. The temperature on the side of the refractory brick layer of the furnace is 1150 C, and the temperature on the outer steel surface is 30C. There is a heat loss of 300 W / square meter at the wall of the furnace. It is difficult to prevent the thin air additions between the brick layers and the brick layer and the steel wall. How many mm of brick layers is the total thickness of these air layers equivalent?
A 1-in Sch 40 stainless steel pipe with a thermal conductivity of 45 W/m-K can move 1,000 kg of saturated steam per hour at 150 °C. Refractory material 0.25 inches thick with a thermal conductivity of 0.025 W/m-K insulates the pipe. At a temperature of 25 °C, the pipe is exposed to the outside air. There is a 1135 W/m2 internal heat transfer coefficient.40 W/m2-K is the outside heat transfer coefficient, whereas -K. Suppose that only the radial direction is involved in steady-state heat transfer and that radiation effects are negligible. ✓ Determine how much heat is being lost through these pipes to the environment.a. 399.1 W/mb. 1525.0 W/mc. 618.4 W/md. 1128.7 W/me. none of the above √ How about the insulated pipe's surface temperature?a. 118.5 °Cb. None of the abovec. 101.5 °Cd. 216.3 °Ce. 292.2 °C
Consider a closed cylindrical reactor vessel of diameter D= 1 ft, and length L= 1.5 ft. The surface temperature of the vessel, T1, and the surrounding temperature, T2, are 390 deg. F and 50 deg. F, respectively. The convective heat transfer coefficient, h, between the vessel wall and surrounding fluid is 4.0 Btu/h . ft . ⁰F. Calculate the thermal resistance in ⁰F .h/Btu.